Anak Krakatau has once again changed the geography of Indonesia’s Sunda Strait, with recent eruptions creating new land around the volcano and expanding the island by more than 30 hectares.

Indonesia’s Geology Agency said satellite imagery showed two new land formations resembling small islands near Anak Krakatau following the powerful eruptive episode in early September. Lava flows from the volcano also increased the size of the existing island by approximately 32.8 hectares, or 81 acres.

The changes underline just how rapidly the landscape around one of the world’s most famous volcanoes can evolve.

Satellite images reveal two new formations

The two new formations were detected using Sentinel satellite imagery from the European Space Agency.

According to Indonesia’s Centre for Volcanology and Geological Hazard Mitigation, or PVMBG, the features appeared inside the water-filled Krakatau caldera and were aligned roughly northwest to southeast.

Officials have so far described them cautiously as formations resembling small islands rather than confirming that they will remain permanent.

Fresh volcanic land can be highly unstable and may later be reshaped or even destroyed by waves, erosion or subsequent eruptions.

Still, their appearance provides a striking example of how volcanic activity can create land as well as destroy it.

Anak Krakatau expanded by 32.8 hectares

The Indonesian Geology Agency says lava produced during recent eruptions has added approximately 32.8 hectares to Anak Krakatau.

The expansion followed a prolonged eruptive episode that began late on September 4 and continued for around 25 hours, until shortly after midnight on September 6.

Satellite monitoring showed lava moving toward the northwest, west and southwest from the eruption center.

The volcano had already been extremely active before that event.

Indonesia’s Geological Agency recorded 224 eruptions between July 2 and September 3, followed by the prolonged eruption and additional Strombolian explosions in the days that followed.

The September eruption caused major disruption

Anak Krakatau’s early September activity was not limited to the immediate volcano.

Volcanic ash spread across parts of western Indonesia and forced multiple airports to temporarily halt operations.

Eight airports suspended flights on September 6, including Jakarta’s main Soekarno-Hatta International Airport, leaving large numbers of passengers stranded.

By the following day, seven airports remained closed and roughly 341,000 travellers had been affected by cancellations and delays.

All affected airports were later reopened as volcanic ash cleared from major flight routes.

Volcano activity has since decreased

Despite the dramatic changes to the island, the latest official assessment indicates that Anak Krakatau’s activity has declined since the major September eruption.

Indonesia lowered the volcano’s alert level from Level III (Siaga) to Level II (Waspada) on September 21 after monitoring showed a decline in eruptive activity and signs of deflation in the volcano.

Authorities continue to prohibit visitors and residents from entering a 2-kilometer radius around the active center of the volcano.

Officials also continue to warn about hazards including incandescent rock fragments, heavy ashfall and renewed eruptive activity.

Why Anak Krakatau keeps changing

Anak Krakatau — which means “Child of Krakatau” — emerged from the sea decades after the catastrophic 1883 Krakatau eruption destroyed most of the original volcanic island.

Since then, repeated eruptions have caused the volcano to grow, collapse and rebuild itself.

The island underwent one of its most dramatic transformations in December 2018, when a major sector collapse triggered a deadly tsunami in the Sunda Strait.

Because the volcano remains highly active, its shape can change substantially during major eruptive episodes.

The newest land formations are another reminder that Krakatau is not a fixed landscape but an active geological system that is continuously evolving.

Are the new islands permanent?

That remains uncertain.

New volcanic islands and lava-built shorelines can disappear quickly if they are made of loose volcanic material or remain exposed to strong ocean waves.

If future eruptions continue depositing lava in the same area, the new formations could become larger and more stable.

But if activity decreases, erosion could gradually break them apart.

For now, scientists are continuing to study satellite imagery and monitor the volcano to determine how the newly created land evolves.

Anak Krakatau remains closely monitored

Although the alert level has been reduced, Indonesia’s authorities are continuing intensive surveillance of the volcano.

Indonesia has more than 100 active volcanoes and lies along the Pacific “Ring of Fire,” making volcanic eruptions and earthquakes a frequent natural hazard across the archipelago.

Anak Krakatau is considered particularly important because of its location in the Sunda Strait between the densely populated islands of Java and Sumatra.

The appearance of new land around the volcano is not, by itself, evidence that a larger eruption is imminent.

But it provides scientists with valuable information about how magma is moving through the system and how the volcano is rebuilding itself after repeated eruptions.